Heating elements driven by a frequency converter for heating a substance or substance mixture in a device

Abstract

In order to improve a device for heating a substance or mixture of substances, wherein the device has a heater with at least one heating element and at least one control device for controlling the at least one heating element, in such a way that the temperature can be set as precisely as possible even in high temperature ranges, it is proposed that the at least one control device has or consists of a frequency converter.

Description

Technical field

[0001] The invention relates to a device for heating a substance or mixture of substances, wherein the device comprises a heater with at least one heating element and at least one control device for controlling the at least one heating element.

[0002] Furthermore, the invention relates to a plastic pyrolysis plant with at least one device for heating a substance or mixture of substances.

[0003] Furthermore, the invention relates to a method for controlling a heating element of a heater for a device for heating a substance or mixture of substances.

[0004] Furthermore, the invention relates to the use of a frequency converter for controlling a heating element of a heater for a device for heating a substance or mixture of substances. State of the art

[0005] EP 0297424 B1 describes a process for cooling hot pyrolysis gas produced during the pyrolysis of waste material containing plastic, rubber or other hydrocarbons, wherein the pyrolysis oil obtained is cooled by direct heat exchange in at least two cooling stages through which the pyrolysis gas flows successively. Description of the invention: Problem, solution, advantages

[0006] The object of the present invention is to improve a device for heating a substance or mixture of substances, wherein the device has a heater with at least one heating element and at least one control device for controlling the at least one heating element, in such a way that the most precise possible temperature control of the substance or mixture of substances within the device can be achieved even at very high temperatures while avoiding large temperature fluctuations.

[0007] According to the invention, a device for heating a substance or mixture of substances is proposed, wherein the device has a heater with at least one heating element and at least one control device for controlling the at least one heating element, wherein according to the invention the at least one control device has a frequency converter or consists of one.

[0008] The device for heating a substance or mixture of substances can have any suitable form and essentially constitutes a container for holding the substance or mixture. The substance or mixture can be introduced into the container for heating and / or passed or transported through it for heating.

[0009] The device can be part of a system, for example, a water heating system, a die-casting machine, or a plastics melting plant. In particular, the device is part of a plastics pyrolysis plant.

[0010] The substance or mixture can be a solid, a liquid, or in a gaseous state. Preferably, the substance or mixture is fed into the device in a solid state and heated within the device in such a way that the substance or mixture transitions into a liquid or gaseous state.

[0011] According to the invention, a frequency converter is used to control the at least one heating element, supplying the heating element with the set voltage. Depending on the desired target temperature, the output voltage of the frequency converter is varied accordingly.

[0012] Electrical components can, in principle, be used to control heating elements in such devices, allowing them to be regulated within the relevant temperature ranges. For example, simple electrical switching elements, such as solid-state relays, are used for this purpose. In a further development step, PID controllers or thyristor controllers, which can be controlled analogously, were employed. However, in all cases, it has been shown that the temperature deviations or the resulting tolerances, particularly at high temperatures, for example above 350°C, are unacceptably high for many applications.

[0013] The aforementioned electrical components for controlling the heating elements typically need to be set to a relatively high voltage during the heating phase in order for them to switch on at all. However, this often leads to temperatures quickly exceeding the desired temperature during the heating phase, or to precise temperature control or adjustment taking a long time, often several hours. Such control components are particularly inadequate for applications where temperatures must be set with pinpoint accuracy, i.e., with very small fluctuations and tolerances. During the heating process, temperatures often overshoot and must be adjusted up and down repeatedly for extended periods until the desired temperature is precisely reached. This also results in unnecessarily high power consumption.

[0014] Surprisingly, it has turned out that controlling a heating element of a heater using a frequency converter can be accomplished much more precisely and overcomes the aforementioned disadvantages.

[0015] Heating elements essentially represent an ohmic resistance, whereby heat is generated by means of an electric current flowing through them.

[0016] Frequency converters, on the other hand, are typically known for controlling electric motors. From the frequency converter's perspective, the load is not a heating element, but an electric motor, with the rotor generating the rotation.

[0017] To make temperature control even more precise, the frequency converter according to the present invention is parameterized and configured accordingly. For example, a software module can be used to generate output voltages in 0.1-volt increments, which then serve to control the heating element very precisely. This eliminates temperature overshoots and allows the temperature to be regulated to an accuracy of + / - 0.1°C. Only very low voltages, e.g., in the range of 1 to 5 volts, are then required to maintain a desired temperature. Temperature overshoots during heating can also be completely avoided, thereby reducing the heating time to one-third or one-quarter.

[0018] Therefore, another advantage of controlling the heating element with a frequency converter is that, due to the shorter heating time, more precise temperature setting and precise maintenance of a target temperature, at least 50% energy savings can be achieved with very small constant output voltages compared to conventional control with the same heating elements.

[0019] Preferably, the device is elongated, and particularly preferably tubular. It can be arranged vertically, horizontally, or at an angle within a system.

[0020] Preferably, the device has an inlet for introducing the substance or mixture and an outlet for removing the heated substance or mixture. Since the substance or mixture can be chemically altered by heating, the outlet also serves to remove a result produced by heating inside the device. For the purposes of this invention, "removal" also includes the transfer of the heated substance or mixture from the device into another device.

[0021] The inlet and / or outlet can be closable openings, valves, or similar devices. The inlet and outlet are preferably located on opposite sides of the device. This allows the substance or mixture to be continuously heated as it moves from the inlet to the outlet.

[0022] It is also preferably provided that the device includes an internal conveying system for transporting, conveying, or passing the substance or mixture. The conveying system can, for example, be designed as a screw conveyor. The conveying system serves to transport the substance or mixture from the inlet to the outlet. It thus conveys the material from the inlet to the outlet along a predetermined conveying axis. The material, i.e., the substance or mixture, is guided along the inner wall of the device to generate heat in this area through the heating elements arranged on the outer wall.

[0023] For this purpose, at least one heating element is preferably arranged on an outer wall of the facility.

[0024] The heating system preferably comprises several individually controllable or individually controlled heating elements. The temperatures can be set individually and differently for each section within the unit. For example, each individual heating element can be set to a different target temperature. Preferably, several control units with frequency converters are also provided for the individual control of each heating element.

[0025] The heating elements are preferably arranged one behind the other and / or side by side along the outer wall of the device. In the case of an elongated or tubular device, the heating elements are preferably arranged around the tube and one behind the other.

[0026] By providing a large number of heating elements along the conveying direction from inlet to outlet, an increasing target temperature can be set and the substance or mixture of substances can be continuously heated as it is conveyed through the device.

[0027] Preferably, the heater is equipped with temperature sensors for measuring the actual temperature of the substance and / or mixture. These temperature sensors extend into an interior space of the device and are electrically and / or communicatively connected to the at least one control unit. The temperature sensors measure the actual temperature at various points inside the device. This measured temperature then serves as an input signal for the control unit to regulate the desired setpoint temperature in that section of the device. For this purpose, the voltage for the corresponding heating element is adjusted using a frequency converter.

[0028] Furthermore, it is preferably intended that the device is completely encased with the heating elements.

[0029] The at least one heating element is preferably designed as a heating sleeve. For example, the heating element can be designed as a multi-phase, in particular 3-phase, heating sleeve. The three phases of the heating element are then connected, for example, to the outputs U1, V1 and W1 of the frequency converter.

[0030] According to the invention, a plastic pyrolysis plant is further provided with at least one previously described device for heating a substance or mixture of substances. The at least one previously described device is designed as a reactor tube for the thermochemical decomposition of organic compounds by targeted heat application under complete exclusion of oxygen.

[0031] The plastic pyrolysis plant is used for the thermochemical decomposition of organic compounds through targeted heat application at temperatures exceeding 350°C. This leads to the breaking of bonds within large molecules in the complete absence of oxygen. Its primary function is to process PE- and PP-containing plastic waste, primarily to obtain pyrolysis oil and gas.

[0032] A plastics pyrolysis plant is therefore a process engineering facility for processing plastic waste (polyolefins) to recover valuable materials such as high-quality oils, gases, diesel, and carbon. Possible substances or mixtures include LDPE, HDPE, LLDPE, PP, PP+C, and / or PE.

[0033] The plastics pyrolysis plant operates on the basis of the thermochemical decomposition of organic compounds at temperatures exceeding 350°C. For example, the substance or mixture inside the reactor tube is heated to a temperature range between 400°C and 600°C using the heating system described above. This process differs from gasification and combustion because it occurs solely through heat and in the absence of oxygen. Gases, liquids, and solids are produced, with the proportions and composition depending not only on the specific material but also on the process temperature, the added additives, the pressure conditions, and the treatment duration.

[0034] The input material is introduced into the reactor tube via an inlet nozzle. Inside the reactor tube, the material is transported by a conveying system and mixed to ensure optimal heat transfer. The outer wall of the reactor tube is heated by heating elements in the form of electric heating sleeves. Once specific temperature thresholds are reached, the pyrolysis process begins inside the reactor tube. During this process, the molecular bonds of the material are broken down, resulting in short-chain molecules.

[0035] Preferably, the plastic pyrolysis plant comprises several of the aforementioned devices connected in series. Following the first reactor tube, the material is conveyed into a second reactor tube. Within the second reactor tube, which is constructed like the first reactor tube and thus the aforementioned device, the substance or mixture is also transported and mixed via a conveying system. Pyrolysis gas produced after heating exits the respective reactor tube via a riser pipe. Remaining solids from the pyrolysis process are collected at the end of the second reactor tube via a solids discharge.

[0036] The pyrolysis gas is then liquefied in condensation steps in a high-temperature condenser and a low-temperature condenser. Cooling is achieved via an indirect circuit. The condensed oil fractions from the two condensation stages can then be automatically conveyed to appropriate storage tanks. Non-condensable components of the pyrolysis gas are purified with water within the system.

[0037] According to the invention, a method for controlling a heating element of a heater for a previously described device is further provided, wherein the heating element is controlled by means of a control device and the control device includes, or consists of, a frequency converter. An electrical voltage is set by means of the frequency converter and the heating element is applied.

[0038] The control unit also includes a software module that generates an output voltage at the frequency converter in as few voltage steps as possible, for example, in 0.1-volt increments, which allows the heating element to be controlled precisely. This prevents temperature overshoot, especially during the heating phase, and enables the desired final temperature to be set precisely and very quickly.

[0039] Preferably, the electrical resistance of a heating element winding is continuously measured using a frequency converter. This allows for the early detection of heating element failure. In heating elements with multiple windings, it is also possible to detect changes in the resistance of individual windings that cause them to diverge from one another. This, too, indicates an impending heating element failure. By using a frequency converter to control the heating elements, additional measuring devices are unnecessary. The frequency converter can simultaneously and continuously measure and monitor the resistance of the heating element winding.

[0040] According to the invention, the use of a frequency converter for controlling a heating element of a heater for a previously described device is also provided. Brief description of the drawings

[0041] The invention is explained below by way of example using preferred embodiments. The schematic representations show: Figure 1: a perspective view of a device for heating a substance or mixture of substances, Figure 2: a perspective view of a section of a device for heating a substance or mixture of substances, and Figure 3: a simplified representation of components of a plastic pyrolysis plant. Preferred embodiments of the invention

[0042] Figure 1 Figure 1 shows a schematic representation of a device 100 for heating a substance or mixture of substances. The device 100 is tubular in the form of a reactor tube for a plastic pyrolysis plant 200 (for clarity shown in Figure 1). Figure 1(not shown) is designed. The device 100 has an internal conveying device 16 for conveying a substance or mixture to be heated. The conveying device 16 is designed in the form of a screw conveyor and is Figure 1 Only shown in principle in the middle of the facility 100.

[0043] The device 100 has an inlet 14 and an outlet 15. By means of the conveying device 16, the substance or mixture supplied at the inlet is conveyed longitudinally through the device 100 to the outlet 15.

[0044] The substance or mixture of substances passed through the device 100 is continuously heated by means of several heaters 10. Each heater 10 has a separate heating element 11 and a control unit 12. The control unit 12 includes a software module 18 which detects the actual temperature in a section inside the device 100, as determined by a temperature sensor 17, and controls the frequency converter 13 of the control unit 12 accordingly. The frequency converter 13 then applies a precise output voltage to the heating element 11 to regulate the temperature in this section inside the device 100 as accurately as possible.

[0045] The heating element 11 is arranged as a heating sleeve and completely surrounds the tubular device 100. For clarity, in Figure 1Only three heaters 10, each with a heating element 11, are shown.

[0046] Preferably, the heating elements 11 are arranged longitudinally in the tubular device 100 such that they are directly adjacent to one another and heat the outer wall of the device 100 in a longitudinal direction. The target temperature can be continuously regulated from the inlet 14 to the outlet 15.

[0047] Figure 2 For better overview, an excerpt from the in Figure 1The depicted device 100, in this excerpt of which only a section of the device 100 is shown, including a heater 10 and a heating element 11. The heating element 11 is designed as a three-phase AC heater in the form of a heating sleeve and is arranged completely around the tubular device 100. The three-phase heating sleeve is supplied with voltage via the three output voltages U1, V1, and W1 of the frequency converter 13.

[0048] In Figure 3 This is a simplified representation of a section of a 200-unit plastic pyrolysis plant. Figure 3 Only the components of the plastic pyrolysis plant 200 that are essential for the invention are shown.

[0049] Examples include: Figure 3Two devices 100 connected in series for heating a substance or mixture of substances are shown. A valve 20 is arranged between the two devices 100. The substance or mixture of substances is fed into the inlet 14 of the first device 100. Within the first device 100, the substance or mixture of substances is heated longitudinally by means of a Figure 3 The gas is conveyed through the conveying unit 16 (not shown) and continuously heated by means of the heating elements 11 arranged on the outer wall. The same process occurs in the second unit 100 located downstream. After passing through the second unit 100, the generated pyrolysis gas is fed to a condenser 22. The remaining solids are collected via a solids discharge 21. Reference symbol list

[0050] 100 Device for heating a substance or mixture of substances 200 Plastic pyrolysis plant 10 Heater 11 Heating element 12 Control unit 13 Frequency converter 14 Inlet 15 Outlet 16 Conveyor 17 Temperature sensor 18 Software module 20Valve 21Solids discharge 22Condenser

Claims

1. Device (100) for heating a substance or mixture of substances, wherein the device (100) has a heater (10) with at least one heating element (11) and at least one control device (12) for controlling the at least one heating element (11), characterized by that which includes at least one control device (12) that has or consists of a frequency converter (13).

2. Device (100) according to claim 1, characterized by that the device (100) is elongated, in particular tubular.

3. Device (100) according to claim 1 or 2, characterized by that the device (100) has an inlet (14) for introducing the substance or mixture of substances and an outlet (15) for removing the heated substance or mixture of substances and / or for removing a result produced by heating inside the device.

4. Device (100) according to any one of the preceding claims, characterized by that The device (100) has inside a conveying device (16) for conveying the substance or mixture of substances through the device.

5. Device (100) according to any one of the preceding claims, characterized by that that at least one heating element (11) is arranged on an outer wall of the device (100).

6. Device (100) according to any one of the preceding claims, characterized by that the heating system (10) has several individually controllable or individually controlled heating elements (11).

7. Device (100) according to claim 6, characterized by that the heating elements (11) are arranged one behind the other and / or next to each other along the device (100) on its outer wall.

8. Device (100) according to any one of the preceding claims, characterized by thatthe heater (10) has temperature sensors (17) for measuring the actual temperature of the substance and / or mixture of substances, wherein the temperature sensors (17) protrude into an interior of the device (100) and are electrically and / or communicatively coupled to the at least one control device (12).

9. Device (100) according to one of claims 7 or 8, characterized by that the device (100) is completely encased with the heating elements (11).

10. Device (100) according to any one of the preceding claims, characterized by that that at least one heating element (11) is designed as a heating sleeve.

11. Plastic pyrolysis plant (200) with at least one device (100) for heating a substance or mixture of substances according to one of the preceding claims, characterized by thatwhich includes at least one device (100) designed as a reactor tube for the thermochemical cracking of organic compounds by targeted heat application under complete exclusion of oxygen.

12. Plastic pyrolysis plant (200) according to claim 11, characterized by that The plastic pyrolysis plant (200) has several units (100) connected in series.

13. Method for controlling a heating element (11) of a heater (10) for a device (100) according to one of claims 1 to 10, wherein the heating element (11) is controlled by means of a control device (12), characterized by that the control device (12) has or consists of a frequency converter (13), wherein an electrical voltage is set and applied to the heating element (11) by means of the frequency converter (13).

14. Method according to claim 13, characterized by thatThe electrical resistance of a winding of the heating element (11) is continuously measured using the frequency converter (13).

15. Use of a frequency converter (13) for controlling a heating element (11) of a heater (10) for a device (100) according to any one of claims 1 to 10.

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